The feeling mounting in the Conservative Party is that Mr Johnson is effectively immune from being sacked.

And Mrs May's allies indicate that she won't give him the satisfaction of being cast out and reinvented as a "Brexit martyr", if that is indeed what he wants.

They seem reassured for now that by keeping him in post, he is less of a danger.

His pronouncements on the EU and issues such as public sector pay are attracting criticism among MPs and his former allies in Cabinet who will, of course, have a key role in choosing the next Tory leader.

Certainly, Tories I've spoken to at conference - including arch-Brexiteers - worry that Mr Johnson's interventions risk making Mrs May look weak in Europe and will simply hand opportunities to Labour.

One of Mr Johnson's biggest critics in Cabinet is Home Secretary Amber Rudd, who accused him of backseat driving over Brexit.

And she is now revealed to have hired the Conservative super-strategist Lynton Crosby to help her retain her Hastings and Rye seat at the next General Election, where her wafer-thin majority is the subject of a targeted campaign by Jeremy Corbyn supporters' group Momentum.

The move will be seen by colleagues as manoeuvring for a future leadership contest, whenever it comes.

There were reports already that Ms Rudd was being supported as a potential candidate by David Cameron and George Osborne following the snap election result in June, until it became clear Mrs May was staying on in Number 10.

If a Tory leadership contest comes after 2019 and into the proposed Brexit transition period, it may be that Ms Rudd's vision of a Britain more closely aligned with the EU could win out.

The jostling for position may be contained here in Manchester, but since losing her majority, danger for the Prime Minister lurks everywhere.

Image:Amber Rudd could be manoeuvring for a future leadership contest

The former Tory minister Matthew Parris warned in The Times on Saturday: "This Conservative Government is finished.

"Over. Toast. Dead meat. Broken. Sunk. Wrecked.

"They can do what they like, think what they like, announce what they like, promise what they like but it's useless now, it's all too late."

The Conservatives are in Government but in the words of one former adviser seem to be in the grip of a "crisis of confidence".

Cabinet ministers are warning Mr Corbyn and Labour's success means the battle of ideas between free markets and nationalised industries needs to be re-fought.

Promising to freeze tuition fees at £9,250, when Labour has vowed to abolish them; to raise the public sector pay cap for some when Labour wants to do so for all; and put £10billion into the Help to Buy scheme, which some Conservatives privately say would be better spent on building new homes, are policy announcements that have not set the conference alight.

Image:Boris Johnson is attracting criticism among MPs and his former allies in Cabinet

Some MPs angrily retort the Prime Minister is focusing on what is deliverable - as responsible leaders should - while Labour just has a wish list; that voters want quiet competence rather than the promise of overturning the economic order.

Mrs May defended her approach on Tuesday morning, saying that "of course the Prime Minister is in charge", while claiming strong leadership is "not about having a Cabinet full of yes men" but a variety of voices.

Mr Johnson might beat a retreat from his Brexit interventions later on Tuesday - having suddenly declared on Monday night that he in fact supported "every dot and comma" of the Prime Minister's approach set out in her Florence speech.